Patients suffering from a variety of illnesses often need to take nutrition by a route other than through the alimentary canal. Patients requiring surgery, patients in comas, patients with digestive tract illness, patients in shock, and patients undergoing healing processes often receive parenteral administration of carbohydrates along with various combinations of lipids, electrolytes, minerals, vitamins and amino acids. Typically this administration is accomplished by intravenous injection or infusion although subcutaneous, intramuscular, peritoneal or other routes may also be used.
When health care professionals administer parenteral nutrients to patients, they take care to avoid blood sugar overload (hypoglycemia). In many cases, even those involving patients with healthy metabolisms, parenteral nutrition can be accomplished and blood sugar levels appropriately maintained through co-administration of insulin. This administration sometimes, however, has serious drawbacks, since insulin has a short half-life and can cause significant variation in the blood sugar levels. Consequently, in serious cases where patients are to receive a high amount of glucose loading, their blood glucose levels are usually titrated and they receive corresponding infusions of insulin to balance the blood glucose level. This titration procedure is both tine consuming and requires a significant expense since the insulin infusion preferably is continuous and has to be controlled by serial blood sugar measurement.
It is well-established that patients suffering from malnourishment benefit greatly from rapid delivery of high amounts of nutrients. Usually, oral routes are used for such nutrition so that the health and function of patients' digestive processes are maintained. When a non-oral route for nutrition must be used, the risk of hyperglycemia and the attendant deleterious effects upon osmolarity, kidney tissue, retinal tissue, blood vessels, and the cardiovascular system are great even if insulin co-administration is practiced. Consequently, the traditional nutrition therapies, which often do not use insulin, call for very low rates of nutrient parenteral administration. When a typical patient receives such parenteral nutrition, the rate of administration is maintained at a low value so that the blood sugar (glucose) level does not exceed the normal physiological range of approximately 60 to 150 mg per dl. These low rates of administration provide an appropriate safety factor to avoid hyperglycemia. Usually, the rates range from 50 to 150 ml per hour of a 5 to 40 wt/wt. % glucose solution.
Nevertheless, nutrition is a fundamental requirement to enable patient healing and sustenance. If patients cannot receive adequate nutrition, as many times occurs with traditional parenteral nutrition, healing takes longer and ancillary problems associated with the patient's primary malcondition often occur. Therefore, there often is a need to deliver parenteral trition to a patient at as high a rate as possible while avoiding the deleterious effect of hyperglycemia and avoiding the need for repetitive or continuous insulin administration and titration.